Magnet for an ionic drive for space vehicles
Patent 7354021 Issued on April 8, 2008. Estimated Expiration Date: 
June 1, 2027. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
June 1, 2027. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesVariable strength beam line multipole permanent magnets and methods for their use Radially magnetized cylindrical magnet H591 Field adjustable transverse flux sources Apparatus for fabrication of permanent magnet toroidal rings Fabrication of permanent magnet toroidal rings High-field, permanent magnet flux source Hollow cylindrical magnetic flux source for image detectors Light-weight magnetic field sources having distortion-free access ports Magic sphere providing distortion-free access to a large internal working space containing a uniform high-intensity magnetic field InventorAssigneeApplicationNo. 11809631 filed on 06/01/2007US Classes:244/171.1, With propulsion60/202, Ion motor335/306, Plural magnets250/396ML, Magnetic lens335/302, Permanent magnets29/607, Including permanent magnet or core425/3, WITH DIRECT APPLICATION OF MAGNETIC FORCE TO MANIPULATE SHAPING MEANS OR WORK264/427, Producing or treating magnetic product precursor thereof335/217, Temperature-responsive type (e.g., temp. compensation means)315/382, With focusing of ray315/4, Inductor or distributed parameter-type inductive structure335/284For magnetizing or demagnetizingExaminersPrimary: Barrera, Ramon M.Attorney, Agent or FirmInternational ClassesB64G 1/40H01F 7/02 DescriptionGOVERNMENT INTERESTThe invention described herein may be manufactured, used, imported, sold, and licensed by or for the Government of the United States of America without the payment to me of any royalty thereon. FIELD OF THE INVENTION The present invention relates to magnetic propulsion systems. More particularly, the present invention relates to devices and methods providing a magnetic field for space vehicle thrusters. BACKGROUND OF THE INVENTION The proposed propulsion systems for ion Hall propulsion of long range space vehicles generally require a radially oriented magnetic field in a toroidal cavity. However, the standard sources of such radially oriented magnetic fields are neithersufficiently uniform nor strong enough to provide the necessary operational efficiency. FIG. 1 depicts the cross-section of a prior art toroidal magnetic structure with a principal axis 17 having a radial magnet 11, outer magnetic coil 12, lens 13 andanode 14 that generates a radial magnetic field with field lines 15. This prior art structure can supply an adequate radial field component for only marginal operational efficiency in the direction of arrow 16 along thruster axis 17. The FIG. 1 priorart structure operates with only marginal efficiency because it is hampered by the undesired axial field components 18 and minimal field strength. Other types of magnetically-generated propulsion systems are needed to overcome the drawbacks ofinefficient operation caused by undesired axial field components and a weak magnetic field. The drawbacks and deficiencies of inefficient operations, unwanted axial magnetic field components and weak magnetic fields found in prior art magnetic propulsion systems could be alleviated with a magnetic structure that generates a strongerradial magnetic field suitable for a more efficient magnetic propulsion. Those skilled in the art will readily observe that a number of potential magnetic structures with differing shapes and geometries could be employed to provide an enhanced magneticfield for a magnetic propulsion system such as the magic ring or magic cylinder, but the conventional prior art magnetic structures also suffer from a number of drawbacks and shortcomings such as excessive weight or cumbersome size. Thus, there has been a long-felt need to develop a new magnetic structure that is suitable for a magnetic propulsion system and does not suffer from the drawbacks, deficiencies, shortcomings and disadvantages of prior art magnetic structures. Upuntil now, this long-felt need for a new structure for a magnetic propulsion system has not been answered. SUMMARY OF THE INVENTION One promising approach that deserves further consideration is the prior art magic toroid. Referring now to FIG. 2, there is depicted a magic toroid with an outer shell 21, hollow central cavity 22 and radial magnetic field, represented by largearrows 23. The magic toroid is a cylindrical magic ring that has been configured into a hollow toroidal shape. One approach for fabricating toroidal magnetic structures is described in this inventor's U.S. Pat. No. 4,911,627 entitled "Apparatus ForFabrication Of Permanent Magnet Toroidal Rings," which is incorporated herein by reference. The main advantage of the magnetic, or "magic," toroid is that it is capable of producing relatively strong uniform radial magnetic fields with minimalstructural masses. Despite these advantages, the magic toroid is a completely closed structure that does not provide an exit for an anion beam. These drawbacks cannot be overcome by merely cutting a circular exit port at the top of the structure because that wouldboth decrease and distort the internal radial magnetic field. This inventor's U.S. Pat. No. 5,396,209 entitled "Light-Weight Magnetic Field Sources Having Distortion-Free Access Ports," points to a number of possible solutions for the magic toroid'slack of either an exit port or working space access. That invention's spherical and cylindrical magnetic structures provide distortion-free access to the working space with spherical and cylindrical cavities, and this approach could also be used with atoroidally shaped magnet to resolve the long-standing shortcomings, drawbacks and disadvantages of prior art magnetic propulsion systems. The toroidally-shaped ionic drive magnet of the present invention advantageously includes a distortion free exitport that is not available in prior art magnetic structures. It is an object of the present invention to provide a toroidally shaped magnetic device with a distortion-free exit port. It is another object of the present invention to provide a toroidally shaped magnetic device with distortion-free exit ports in order to provide a more operationally efficient, uniform and stronger radial magnetic field. It is still a further object of the present invention to configure a toroidally shaped magnetic device with distortion-free exit ports to release unwanted electrons from a central cavity in order to provide for a more operationally efficient,uniform and stronger radial magnetic field that does not interfere with a vehicular propulsion system. It is yet another object of the present invention to provide a method for forming a toroidally shaped magnetic device with distortion-free exit ports in order to provide a more operationally efficient, uniform and stronger radial magnetic field. These and other objects and advantages are accomplished by this invention's toroidally-shaped magnetic device for propulsion systems, comprising a section of a magic cylinder magnetized in a cylindrical direction that is added to a uniformlymagnetized cylindrical shell with no magnetic field in its central cavity to produce a cylindrical shell with a uniform interior magnetic field configured in such a way that a slot can be removed from the cylindrical shell for an exit port, whichstructure is then bent to form a toroidally-shaped ionic drive magnet. The present invention also encompasses a magnetic propulsion system for space vehicles and methods for magnetizing a toroidal ionic drive structure for a vehicle. BRIEFDESCRIPTION OF THE DRAWINGS FIG. 1 depicts a cross-sectional view of a prior art magnetic structure that generates a radial magnetic field; FIG. 2 depicts a cut-away view of a prior art radial magic toroid magnetic structure; FIGS. 3A-3C illustrates cross-sectional side views of selected magnetic structures and combined directions of magnetization; FIG. 4 depicts a cross-sectional view of a composite cylindrical magnetic segment of the present invention; and FIG. 5 depicts a front perspective view of the toroidal ionic drive magnet of the present invention. DETAILED DESCRIPTION OF THE DRAWINGS The present invention resolves the long-standing problems, shortcomings and limitations of prior art magnetic propulsion systems caused by undesired axial field components and a weak magnetic field by assembling a group of magic cylinder sectionsthat are magnetized in a cylindrical direction and then added to a uniformly magnetized cylindrical shell without a central magnetic field. By assembling magic cylinder sections with a cylindrical magnetization direction into a uniformly magnetizedcylindrical shell without a central magnetic field, this invention's cylindrical magnetic segments produce a cylindrical shell with a uniform interior magnetic field from which a slot can be advantageously removed to construct an exit port. Thecylindrical magnetic segments are then bent to form this invention's toroidal ionic drive magnet. Referring now to FIGS. 3A-3C, the present invention's toroidal ionic drive magnet can be better understood by comparing cross-sectional views of three selected magnetic structures. FIG. 3A depicts a cross-sectional side view of a magic cylindersection 31, FIG. 3B is a cross-sectional side view of a uniformly magnetized cylindrical shell 34 and FIG. 3C is a cross-sectional side view of a composite cylindrical magnetic structure 37. The FIG. 3A magic cylinder section 31 is magnetized in thedirections of the small arrows 32 according to the formula: γ=2θ Equation (1) where θ is the coordinate angle and γ is the angle of magnetization with respect to the polar axis with an interior magnetic field represented bylarge arrow 33. The FIG. 3B uniformly magnetized cylindrical shell 34 is magnetized in the directions of small arrows 35. Those skilled in the art will readily appreciate that the FIG. 3B uniformly magnetized cylindrical shell 34 produces no interiormagnetic field in the central cavity 36. Adding the magnetization vectors of the FIG. 3A magic cylinder section 31 to those of the FIG. 3B uniformly magnetized cylindrical shell 34 results in the FIG. 3C composite cylindrical structure 37, which produces the same uniform interiormagnetic field, represented by large arrow 41, in its interior central cavity 38 as that produced by the FIG. 3A magic cylinder section 31. The FIG. 3C composite cylindrical structure 37 is also magnetized in a cylindrical direction, as represented bysmall arrows 38, with a central cavity 39 and a uniform interior magnetic field 41 in the central cavity 39. Note, however, that after the vector addition, the slot 40 section, depicted by the broken lines, of the composite cylindrical structure 37 atthe magnetic equator requires no magnetization so that that slot 40 portion of the composite cylindrical structure 37 can be removed without disturbance, reduction or distortion of the interior magnetic field 41 to provide the necessary exit port forescape of unwanted electrons from the central cavity 39 of the composite cylindrical structure 37. The small arrows 38 all have unequal lengths, which indicates a varying magnetic strength. If the largest possible magnetization strength were used at all points of the magnetic structure, one could leave the magnetic field unaltered if materialwere pared away to compensate for the greater strength according to the formula: ƒ×ƒ×× ##EQU00001## where Br is the magnetic remanence of the magnetic material and ro and ri are the outer and inner radii, respectively. The result is the single magnetic segment 45 depictedin FIG. 4. Referring now to FIG. 4, there is depicted a cross-sectional view of a single cylindrical magnetic segment 45 of this invention's toroidal magnetic structure before being formed into a toroid with multiple cylindrical magnetic segments 45. Thecylindrical magnetic segment 45 is magnetized in a cylindrical direction, as represented by small arrows 46, with a central cavity 47 and a uniform magnetic field 48. The small arrows 46 all have unequal lengths, which indicates a varying magneticstrength. Referring now to FIG. 5, there is depicted the toroidal ionic drive magnet 50 of the present invention, comprising multiple FIG. 4 cylindrical magnetic segments 45 bent into a toroidal tube with ports A and B. Material can be removed from eitherthe FIG. 4 cylindrical magnetic segment 45 at point A or point B of the outer surface prior to assembly without changing the interior magnetic field 48 appreciably because at these locations the magnetic material is thin and its contribution to theinterior magnetic field 48 is minimal. Similarly, the material at point A and point B of the outer surface could also be removed from assembled FIG. 5 toroidal ionic drive magnet 50 for the same reason. Of course, the wider that the slots at point Aand point B are cut, the more magnetic field reduction and distortion will result. If point A is chosen as the exit slot location, than a second slot at point B could also be useful for the insertion of a copper or high conductivity heat conduit fromthe interior where considerable heat is generated from formation of plasma. The exit port at point A is a critical feature of this invention because unwanted electrons are then forced into a circular orbit in order to eliminate interference with thepropulsion of the vehicle. The present invention also encompasses a toroidal magnetic ionic drive system for a space vehicle and a method for magnetizing a toroidal ionic drive structure for a vehicle. The method for magnetizing a toroidal ionic drive structure for avehicle comprises the steps of forming a group of magic cylinder sections; forming a uniformly magnetized cylindrical shell having a central cavity and a first plurality of magnetization vectors; providing a vehicle with a propulsion system; magnetizingthe group of magic cylinder sections in a cylindrical direction, with each magic cylinder section having an interior magnetic field and a second plurality of magnetization vectors; affixing the group of magic cylinder sections to the cylindrical shell;combining the first and second plurality of magnetization vectors; forming a group of composite cylindrical magnetic segments, each composite segment, being magnetized in a cylindrical direction with a varying magnetic field, having a central cavity anda uniform interior magnetic field; bending the group of composite segments into a toroidal tube; removing a first slot section from an outer surface of the toroidal tube; providing a longitudinal exit port; and allowing electrons to escape from thecentral cavity without distorting the uniform interior magnetic field in order to eliminate unwanted interference with the propulsion system. A number of variations of the devices and methods of the present invention are also possible, including differences in the FIG. 5 toroidal form and methods that sacrifice minimal mass for ease of manufacture. It is to be further understood thatother features and modifications to the foregoing detailed description are within the contemplation of the present invention, which is not limited by this detailed description. Those skilled in the art will readily appreciate that any number ofconfigurations of the present invention and numerous modifications and combinations of materials, components, arrangements and dimensions can achieve the results described herein, without departing from the spirit and scope of this invention. Accordingly, the present invention should not be limited by the foregoing description, but only by the appended claims. |
